The UN Security Council has condemned a deadly bombing in the Belarus capital, but called it an "apparent" terrorist attack in a move diplomats said cast doubt on the official version of events.

The attack in the Minsk metro on Tuesday killed 12 people and injured 200. President Alexander Lukashenko said three suspects had confessed to the bombing and threatened new action against the Belarus opposition.

The United States, with the backing of other Western nations, insisted on adding the word "apparent" to the normally routine Security Council statement issued after attacks, diplomats said.

"The word 'apparent' is included in this statement for a reason," said one diplomat from the 15-nation council, speaking on condition of anonymity.

"There are credible indications in Belarus saying there is a more than even chance that the government was behind this."

"There was a lot of debate about this statement which is why it came out so late. But it just highlights international suspicions," added a diplomat from a second nation, also speaking on condition of anonymity.

"The members of the Security Council condemned in the strongest terms the apparent terrorist attack that occurred in Minsk, Republic of Belarus, on April 11, 2011, causing numerous deaths and injuries," said the statement finally released on Wednesday.

"They expressed their deep sympathy and condolences to the victims of this heinous act and to their families, and to the people and government of the Republic of Belarus," it added.

In a statement expressing "sincerest condolences to the people of Belarus," UN secretary-general Ban Ki-moon referred to "an explosion" at the Minsk metro station. Mr Ban is normally an explicit critic of terrorist outrages.

The US State Department condemned the bombing on Tuesday but avoided calling it terrorism. A statement released by the French foreign ministry also used the term "explosion."

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